In recent years, public interest in competitive sporting activities has increased substantially. Not only are more individuals watching popular spectator sports such as football, baseball and basketball; but also, more and more people are becoming actively involved in regularly playing a large number of competitive sports.
Where more and more individuals are actually playing or attempting to play a particular sport, increased interest is frequently noticed in the problems of how to learn to play; how to improve one's acquired ability to play; and how to avoid any injury to oneself due to play. Considerable basic skills must be acquired by the novice player in most sports, without which proficiency at the game usually suffers and physical injury may result. For example, in the game of tennis a proper grip on the racquet is necessary to enable the player to deliver optimum force to the ball when striking it and to prevent the player from injuring a hand or wrist due to reactive forces generated when the ball is struck.
Also, the location on the strung portion of the racquet at which the ball is struck plays an important role. If the racquet is held with the plane of its strings approximately perpendicular to the path of the racquet as it approaches the ball and if the ball strikes the racquet in approximately the center of the strung area, then the ball will leave the racquet with optimum velocity and the racquet will not twist in the player's hand. However, if the ball strikes the racquet at a location spaced from the center of the strung area, the racquet usually will twist the player's hand about the wrist or snap the hand back toward the elbow, so that the ball leaves the racquet at an undesired angle and less than optimum speed. Another serious effect of such improper hitting of a tennis ball is that the repeated twisting of the arm and snapping of the wrist frequently lead to the injury commonly known as "tennis elbow". Thus, tennis players and coaches have long sought a device or technique for reliably training players to hit the ball consistently in the center or "sweet" part of the strung area, both to improve their game performance and to minimize the likelihood of injury.
In other sports where a ball or other playing or game element is struck by some sort of club, bat, racquet or similar athletic instrument, players also seek to strike the game element with a preferred portion of the instrument at which an optimum "hit" is obtained without undesirable side effects on the player. In addition to tennis, games such as golf, jai lai, ping pong, badminton, baseball, polo, softball, lacrosse, cricket and hockey, all involve the use of an athletic instrument for striking a ball or game element. In each case, the location on the instrument at which contact is made greatly affects the resultant movement of the game element and the reactive force transmitted to the player.
Under these conditions, it is apparent that a need exists for a device or means which will enable a player to know immediately whether the ball or game element has been struck with the proper portion of the athletic instrument. This type of prompt feedback enables the player to correct his swing accordingly. Such a device would facilitate the training of new players and would enable experienced players to improve their game considerably.